A few short weeks after John cut the romance short, the pair seem to be riding high this week and Katy's getting so attached her friends worry she'll get a fresh heartbreak — but this time from the guitar-slinging lothario.

“At first, she was quite careful with John and said she wasn’t ready for a relationship and just wanted to have fun," a friend told RadarOnline.com. "But now she appears to have fallen dangerously in love with him and her friends are concerned."

Her pals predict John roped her back in promising he'd changed, and she's "slowly warming" to the idea he's boyfriend material. However, they don't buy the character evolution and think this is just another trademark, Mayer-approved womanizing move.

“He’s never been short of female attention in the past and has always been quick to milk that at every given opportunity," the source reveals. "But John realizes now that it made him appear a bit of a douche bag and an unattractive catch…he knew he had to change his ways."

Those close to her say she's fantasizing about visiting his ranch in Montana and taking the relationship to the next level.

Her deep affections and fantasies should come as no shock, considering Katy told reporters while promoting her biopic, Part of Me, that she's still optimistic about romance despite her recent divorce from Russell Brand.

"I still believe in love, most definitely," she said. "I'm just going to let that take the lead."